Mr Blair wrote: ''By the standards of days gone by I was not even remotely a toper, and I couldn't do lunchtime drinking except on Christmas Day, but if you took the thing everyone always lies about - units per week - I was definitely at the outer limit.

''Stiff whisky or G&T before dinner, couple of glasses of wine or even half a bottle with it. So not excessively excessive. I had a limit. But I was aware that it had become a prop.''

Mr Blair said he could ''never work out'' whether alcohol was good for him because it helped him relax, or bad because he could have been working instead of relaxing.

He came to the conclusion that the benefits of relaxation outweighed the cost to his work.

''I thought that escaping the pressure and relaxing was a vital part of keeping the job in proportion, a function rather like my holidays,'' he wrote.